Electrochromic behavior under circularly polarized light and effect of chiral induced spin selectivity on the electropolymerization process of chiral conducting polymers

The last few decades have seen growing interest in π-conjugated conducting polymer, mostly due their flexibility, processability, and the prospect of tailoring their optical and electronic properties. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most commonly applied conducting polymers, mainly for its electrochromic properties, good conductivity and stability.

The electronic properties of conducting polymers are influenced by micro and macro structural order, which can be tailored by using different side groups. Therefore, the effect of side chains in conducting polymers is extensively studied. However, chiral side chains are far less studied, and many chiral conducting polymers suffer from regioirregular structures, which result in polymer films with inferior properties.^[1] Recently, π-conjugated oligomers and polymers with helical chirality were shown to function as electron spin filters via a chiral-induced spin selectivity (CISS) effect. As this effect provides a way to create spin-polarized electrons without the use of a magnet, it opens new possibilities for molecular spintronics devices.^[2]

In this work, we introduce PEDOT derivative bearing two aromatic stereogenic centers on each monomer (diphEDOT). These side groups are expected to induce π–π interactions, which will allow the study the effect of such interactions on the polymer morphology as well as the optical and chiroptical properties. The enantiopure diphPEDOT show reversible spectroelectrochromic chiroptical properties as recorded in their ECD spectra. We find that the electropolymerization process of enantiopure diphEDOT is affected by the magnet direction when using a magnetic electrode, highlighting the potential of the CISS effect for efficient electro-coating of surfaces with conducting polymers.

References

[1] D. Caras-Quintero, P. Bäuerle, Chem. Commun., 2004, 926-927.

[2] R. Naaman, D. H. Waldeck, Annu. Rev. Phys. Chem. 2015, 66, 263-281.